It is well known that in order to carry out a correct sewing of two articles, these must be properly positioned with respect to means which operate the sewing. For example, to make pantyhose articles, provision is made for assembling two stockings, that is, two knitted tubular articles whose portion in correspondence of the bodice is to be cut longitudinally over a predetermined length and then sewing the articles together in correspondence of the thus cut legs. To this end, the stockings intended to form the pantyhose article are fit on corresponding paired flat support shapes which allow the same stockings to move between loading, positioning, cutting, sewing and unloading stations of a horizontal carrousel machine so-called "pantyhose seamer" or "line-closer". Pantyhose-assembling machines which operate in a manner set forth above are described in the U.S. Pat. Nos. 4,444,140, 5,345,889 and 4,303,026.
Under operating condition, the seamers of these known machines are subjected to continuous motion from and to the articles under formation by means of a mechanical transmission provided with a cam which controls the motion of the support of same seamers. In this way, the seamers are driven, during the articles-sewing step, according to a preset and unchanging scheme. It thus follows that the sewing is always performed in the same way, even if the articles under formation are badly positioned, which hardly allows meeting the requested quality.